Apparatus for selective plating



June 14,1955 v s 2,710,834

APPARATUS FOR SELECTIVE PLATING Filed Oct. 27, 1951 2 Sheets-Sheet 2ATTORNEY FIE E Unit Patented June 141, 1955 APPARATUS FOR SELECTIVEPLATXNG Marcus Vrilakas, Sacramento, (Calif.

Application Gctober 27, 1951, Serial No. 253,526

7 (Ilaims. (U. 204-212) My invention relates to methods and mechanismsfor to leave the previously prepared and protected portions of theobject without any electro deposition.

While this technique has proved to be satisfactory over a long period oftime, especially in connection with smaller objects, it has in recentyears become important to electroplate certain portions of relativelyheavy machinery; for example, internal combustion engine crank shafts.It is deemed advisable to coat the main bearing journals and the crankpin journals with a Wear resistant coating such as chromium but forreasons of economy and for other reasons it is desired to leave thecrank throws and comparable parts without any superficial platingdeposit.

The customary technique of applying paint or the like to those portionswhich are not to be plated requires first a masking of the parts to beplated against the paint, then a painting operation, followed by theplating cycle, and later followed in some instances by a removal of thepaint. All of this is a laborious and costly procedure.

it is therefore an object of my invention to provide a new and improvedmethod and apparatus for selective plating.

A further object of my invention is to provide a plating apparatususeful in connection with crank shafts and the like for plating theselected portions thereof without depositing any plating material on theremaining portions and without necessitating preliminary masking orpaint- 1ng.

A still further object of my invention is to provide a method which canbe utilized in conjunction with most electroplating equipment nowavailable, yet which, when practiced will eliminate the previouspainting or masking operation.

A still further object of my invention is to provide a means and methodfor electroplating certain portions only of an object without requiringprevious preparation of the object.

An additional object of the invention is to provide improved techniqueand means in the plating of objects selectively.

Other objects, together with the foregoing, are attained in theembodiment of the apparatus and in the preferred method of practicingthe invention described in the accompanying description and illustratedin the accompanying drawings, in Which Figure l is a diagram showinggenerally in cross section on a vertical plane an apparatus for use inselective plating and for use in carrying out my method for selectiveplating.

Figure 2 is a similar diagram of a modified form of apparatus.

Figure 3 is a cross section, the plane of which is indicated by the line33 of Figure 2.

While the method and apparatus have been especially successful in theelectro deposition of plating material on automotive crank shafts andwhile they are both described in connection with such an object herein,it will be recognized by those skilled in the art that other objects canequally well be selectively plated in accordance with my disclosure.

In one form of apparatus, as shown in Figure 1, there is provided a tank6 within which an object 7 to be placed can be disposed. The object 7 ispreferably an electrical conductor and is a crank shaft, for example. itcan be mounted for rotation about its major axis in accordance with thecustomary practice, or it can simply be immersed. The crank shaft '7 isvirtually completely submerged in a plating bath contained within thetank 6 which is virtually full of such liquid electrolye.

in accorrdance with my invention, I surround each of the main bearingjournals 8 and 9 with casings 11 and 12, preferably fabricated ofnon-conducting material or electrically insulating material and disposethem so that they come apart in two halves, being fastened by suitablesecuring means 13. The dimensions of the casings 11 and 12. are suchthat they fit accurately around the journals 8 and 9 and come intoabutment with the crank throws 14 and 16 and with the end flanges 17 and13. Each of the casings 11 and 12 is open to the electrolyte in the tank6 by means of apertures 19 and 21, but is otherwise closed.

As an alternative, I disclose on the central crank throw 22 and betweenthe crank cheeks 14 and 16 a casing 23 fabricated of metal but which isprovided with insulating discs 24 and 25 to preclude electrical flowbetween the casing and the material of the object 7 being plated. Thecasings 11, 12 and 23 are otherwise identical.

Disposed inside each of the casings is an electrode 26 which ispreferably an annular form and can be split as are the various casingsthemselves on a horizontal plane. Each of the electrodes 26 is spacedfrom its adjacent part 8, 22 or 9 to be plated and is connected throughan insulating fitting 27 by a conductor 28 to a supply 29 ofelectroplating current. Similarly, the casing 23 has its electrodeconnected through a conductor 31 whereas the casing 12 has its electrodeconnected through a conductor 32 to the source 29. The source ofelectroplating current 29 is any suitably arranged mechanism connectedby leads 33 and 34 to a source of electromotive force.

The remaining portions of the plating circuits are all combined into alead 36 extending from the source 29 to a conductor 37 in directmetallic contact with some convenient portion of the crank shaft 7.

Then the crank shaft with its portions selected for plating suitablysurrounded by cases and connected as shown is immersed in a platingelectrolyte and when the current is caused to flow there is a platingaction that takes place between each of the electrodes such as 26 to theadjacent crank pin such as 8 without current flow being extended to theadjacent portion such as 14 of the crank shaft. The journals themselves,consequently, are covered with a deposit of plating material such aschromium, but the adjacent material such as the throws 14 and 16 are notin any wise plated, being protected by the casings 11 and 12 and 23.

When the plating is completed, the parts are removed from the bath, thecasings are removed, and the job is then finished without the necessityof any further work.

In the modified form of my apparatus for practicing my method as shownespecially in Figures 2 and 3, there is provided a tank 4-1 for thereception of the electroplating bath. This electrolytic liquidsubstantially fills the tank. Immersed in the tank is a crank shaft 42having main bearings 43 and 44 and a crank pin bearing 46.

The crank shaft is preferably supported for rotation within the bath andthat is accomplished by a suitable support 47 and a rotating support 48,conveniently the shaft of a drawing motor 50 so that the shaft isrevolved about its axis 49.

Encompassing the crank pin bearing 46 is a casing 87 having an upperhalf 88 and a lower half 8). The casing is preferably made ofnon-conducting plastic or other comparable material and is pervious tothe electrolyte in that it is made without any top or bottom inclosures.The top half of the casing 88 is cut away as closely as possible toconform to the crank pin diameter and the walls of the top portion ofthe casing are spaced apart by struts 51 and 52. Similarly, the bottomhalf 89 of the casing fits its part of the crank pin bearing relativelywell, abuts the top part of the casing and has its walls held inposition by struts 53 and 54. For convenience in handling, the twohalves of the casing are held in closed position by coil springs 56 and57 engaging lugs 58 and 59 on the two halves so that while the parts arenormally held together to provide a functionally unitary casing, byunhooking the springs the casing can be readily taken apart and takenaway from the hearing.

In order partly to locate the casing but more especially to treat thedeposited material to avoid excrescences or growth or treeing of thematerial being deposited, each of the parts of the casing is providedwith a pair of rollers 61 and 62 turning on pins 63 and 64 mounted inthe casing. As the crank shaft rotates, the rollers roll upon thesurface of the crank pin and insure that a satisfactory plating depositis made.

The plating itself is eifectuated by the medium of a pair of electrodes66 and 67 which are bars often arcuate in transverse cross section whichare dependent between the struts 51 and 52, for example, and the rollers61 and 62, for example. The electrodes are thus loosely confined betweenthe struts and the rollers and the side walls of the casing. Theelectrodes hang freely through the casing and are secured at their upperends to a cross piece 77 to Which the conductor 78 is attached. Thisconductor corresponds to the conductors 28 or 31 or 32 of the Figure 1modification. The cross piece 77 is hung from a hook 79 having a closurehook 81, both adapted to em brace a supporting rod 82 mounted on anyconvenient support.

. In the operation of this device when the current is flowing throughthe plating circuit as disclosed in connection with Figure l, and whenthe crank shaft is rotated in the bath within the tank 41, the casingrises and falls and moves laterally with the rotation of the crank pin,being prevented from rotation with such pm by the interposition, oftheelectrodes 66 and 67. These electrodes swing fromlside to side in thefashion of a pendulum hung from the rod 82 and during this time areeffective to assist in the plating operation. When the plating is beingdeposited, it is kept from the parts of the crank shaft such as thecheeks 42 by reason of the positioning of the surrounding permeable boxor casing 47.

, When the plating operation is completed, the mechanism is removed fromthe bath, the springs 56 and 57 are unsnapped, and the parts are therebyreleasedfrom the crank shaft which is a completely plated and finishedarticle without further work.

I claim:

1. An apparatus for selective plating comprising a tank for containing aplating bath, a pair of parallel elongated electrodes, means above saidtank for suspending said electrodes in said bath for swinging movementon a fixed horizontal axis, a casing of electrically insulating materialextending around said electrodes and in freely sliding relationshiptherewith, said casing being open at the top and bottom and havingalined openings therethrough between said electrodes, means forsupporting an object to be plated extending through said alined openingsand between said electrodes, means for supporting said casing on saidobject, means for moving said object and said casing in said bath in adirection along the length of said electrodes and in a directiontransverse to the length of said electrodes, means for preventing saidelectrodes touching said object, and means for including said object andsaid electrodes in a plating circuit.

2. An apparatus for selective plating comprising a tank for containing aplating bath and for containing an electrically conducting horizontallydisposed shaft, means for rotating said shaft within said tank, saidshaft having a portion eccentric to the axis of rotation, an electrodesupport fixed above said tank, a pair of electrodes hanging from saidsupport into said tank on opposite sides of said eccentric portion ofsaid shaft, an insulating casing open at the top and bottom andextending around but free from said electrodes and extending above andbelow said shaft, said casing being split on a shaft diameter and beingcut out to pass the eccentric portion of said shaft, means forsupporting said casing on the eccentric portion of said shaft, means insaid casing for holding said electrodes away from the eccentric portionof said shaft, means for holding said casing against separation at saidsplit, and means for establishing a plating current between saidelectrodes and said shaft.

3. An apparatus for selective plating comprising a tank for containing aplating bath and for containing an electrically conducting horizontallydisposed shaft, means for rotating said shaft within said tank, saidshaft having a portion ececntric to the axis of rotation, an electrodesupport fixed above said tank, a pair of elongated electrodes supportedon said electrode support for swinging movement in unison across theaxis of rotation and hanging into said tank on opposite sides of saideccentric portion of said shaft, an insulating casing open at the topand bottom and extending around said electrodes and above and below saideccentric portion of said shaft, members extending across and secured tosaid casing and resting on said eccentric portion of said shaft inposition to support said casing on said eccentric portion of said shaftand to hold said electrodes away from said eccentric portion of saidshaft, and means for establishing a plating current between saidelectrodes and said shaft.

4. For use in an apparatus for selectively plating a selected area of arotating shaft. an insulating hollow casing defined by four walls andopen at the top and bottom and being split on a shaft diameter into twohalves, said casing having cut out portions to pass said shaft with saidselected area within said casing, insulating members extending acrossthe interior of said casing and secured to the walls of said casing andadapted to rest on and transfer the weight of saidcasing to said area ofsaid shaft, said insulating members being positioned to hold a straightelectrode extending through the open top and bottom of said casing awayfrom said shaft, and means for releasably holding said casing halvestogether.

5. An apparatus for selective plating comprising a tank for containing aplating bath and for containing an electrically conducting horizontallydisposed shaft having an eccentric portion, means for revolving saidshaft in said bath, a fixed electrode support above said shaft, anelongated electrode depending from said electrode support to swinglaterally and hanging into said tank on one side of the eccentricportion of said shaft, an insulating casing open at the top and bottomand extending around said electrode to abut and swing said electrode inone direction as said shaft is rotated, said casing being split on ashaft diameter into two halves and having cut out portions to pass theeccentric portion of said shaft. insulating means extending across saidcasing between said electrode and the eccentric portion of said shaft inposition to hold said electrode away from said shaft and to abut andswing said electrode in the other direction as said shaft is rotated,means for releasably holding said casing halves together, and means forestablishing a plating current between said electrode and said shaft.

6. An apparatus for selectively plating a crankshaft having a mainbearing and a crank pin bearing comprising a tank for containing aplating bath, means for supporting said shaft within said bath forrotation about the axis of said main bearing with said axissubstantially horizontal, means for so rotating said shaft, a supportingrod above said bath and parallel to said axis, a pair of elongatedelectrodes hung on said rod to swing transversely of said axis, saidelectrodes being spaced apart and of sufficient length to lie onopposite sides of said crank pin bearing in all rotated positionsthereof, an insulating casing open at the top and bottom surroundingboth said electrodes and closely approaching said crank pin bearing,means for supporting said casing on said crank pin bearing, means forkeeping said electrodes away from contact with said crank pin bearing,and means for conmeeting said electrodes and said crankshaft in aplating circuit.

7. An apparatus for selective plating comprising a tank for containing aplating bath, means for supporting a crankshaft in said tank forrotation within said plating bath with the main bearing axis of saidcrankshaft in a fixed horizontal position, said crankshaft having aneccentric crank pin, means for rotating said crankshaft about said mainbearing axis to swing said crank pin in a circle centered on said axis,means above said tank and disposed substantially above said crank pinfor supporting an electrode, an elongated electrode hanging from saidsupporting means and free to swing laterally thereon, means forestablishing a plating current between said electrode and said crankpin, an open end casing of insulating material extending between saidelectrode and the throws of said crankshaft adjacent said crank pin andextending around said electrode and said crank pin, means for supportingsaid casing on said crank pin for sliding movement relative to saidelectrode, and means on said casing for swinging said electrode withsaid casing and for holding said electrode away from said crank pin.

References Cited in the file of this patent UNITED STATES PATENTS827,478 Totten July 31, 1906 1,880,382 Garling Oct. 4, 1932 2,422,242Kaufman June 17, 1947 2,473,290 Millard June 14, 1949 2,530,677Berkenkotter Nov. 21, 1950 FOREIGN PATENTS 925,912 France Apr. 14, 1947563,435 Germany Nov. 5, 1932

1. AN APPARATUS FOR SELECTIVE PLATING COMPRISING A TANK FOR CONTAINING APLATING BATH, A PAIR OF PARALLEL ELONGATED ELECTRODES, MEANS ABOVE SAIDTANK FOR SUSPENDING SAID ELECTRODES IN SAID BATH FOR SWINGING MOVEMENTON A FIXED HORIZONTAL AXIS, A CASING OF ELECTRICALLY INSULATING MATERIALEXTENDING AROUND SAID ELECTRODES AND IN FREELY SLIDING RELATIONSHIPTHEREWITH, SAID CASING BEING OPEN AT THE TOP AND BOTTOM AND HAVINGALINED OPENINGS THERETHROUGH BETWEEN SAID ELECTRODES, MEANS FORSUPPORTING SAID CASING BE PLATED EXTENDING THROUGH SAID ALINED OPENINGSAND BETWEEN SAID ELECTRODES, MEANS FOR SUPPORTING SAID CASING ON SAIDOBJECT, MEANS FOR MOVING SAID OBJECT AND SAID CASING IN SAID BATH IN ADIRECTION ALONG THE LENGTH OF SAID ELECTRODES AND IN A DIRECTIONTRANSVERSE TO THE LENGTH OF SAID ELECTRODES, MEANS FOR PREVENTING SAIDELECTRODES TOUCHING SAID OBJECTS, AND MEANS FOR INCLUDING SAID OBJECTAND SAID ELECTRODES IN A PLATING CIRCUIT.